1. Field of the Invention
The invention relates to a feed comb arrangement for a combing machine comprising an intermittently driven pair of feed rollers preceding the feed comb arrangement in the transport direction of the fiber web to be combed and a take-down arrangement, in particular in the form of take-down rollers, following the feed comb arrangement.
2. Background Art
Conventionally, the feed comb arrangement is formed by a flat feed comb covered with a plurality of needles, which feed comb has the object of transporting the fiber web to be combed in the transport direction to the comb roller and to the nippers arrangement in accordance with and in synchronization with the cycle of the combing operation.
A further object of the feed comb is to compress and retain the fibers out of the transport phase, when the take-down rollers draw the combed fibers off the fiber web. Accordingly, clinging fibers are separated from the fibers to be drawn off by means of the feed comb.
Within a combing operation the course of motion is such that the feed rollers transport the fiber web over a certain distance in the direction of the combing cylinder and of the take-down rollers. This refeeding is effected as a rule in that moment, in which the fibers already combed are drawn off the fiber web retained by the feed comb. The feed comb is closed in this moment and the needles of the feed comb penetrate the fiber web. After completion of the feeding, i.e. of the transport motion by the feed rollers, the feed comb is lifted off the fiber web and moves back by that distance, which corresponds to the transport distance by feed rollers.
The feed comb then pierces again the fiber web through the feed comb grid and carries out a new transport motion for the fiber web. The feed comb remains closed as long as the take-down rollers have drawn off the combed fiber web. A new combing operation is then started and the feed comb opens again and releases the fiber web for feeding the feed comb rollers.
Conventional feed combs are realized such that the needles in the form of needle bars are inserted into a base plate, each needle bar comprising a plurality of needles arranged side by side.
The conventional feed combs embodied in such a manner show a considerable disadvantage in that with respect to the fiber web they act also as a combing element and cleaning element apart from their transport and retain function, so that again and again larger parts of burrs and straw accumulate on the needles of the feed comb. These accumulations grow and are then drawn off in compressed form, while they are often transported through and below the following top comb because of their size and accordingly are left as an impurity in the combed fiber web.
To avoid this, one can only proceed by stopping the combing machine after certain running times, in order to clean the feed comb, which of course results in undesired losses of production.
A further considerable mechanical disadvantage of known feed combs is that within a combing operation they must run through four motion phases in different directions. These motion phases comprise an approximately circular arc-like motion, for leaving the fiber web, a linear motion directed backwards, for being able to initiate a new feeding phase, a further circular motion for piercing the fiber web and then again a linear motion for carrying out transport. Jerky motions of this type with about 200 combing operations per minute result in that a combing machine of the type considered works rather unsteadily.